An impedance matching circuit is used for impedance matching between an antenna and a Radio frequency section. However, if the impedance matching circuit is fixed, impedance mismatching occurs under the effect of a body approaching a radio communication apparatus and it becomes impossible to obtain the essential antenna performance because of a matching loss; this is a problem.
For example, under circumstances where a radio communication apparatus is brought close to the human body of the user for use, since the human body is a lossy dielectric, the antenna characteristic receives the effect of the human body and impedance mismatching occurs. The impedance mismatching state changes in various use circumstances and installation environments such as telephone conversation, electronic mail, and holding the radio communication apparatus in a bag, a pocket, etc.
To solve such problems, an art exists wherein a received signal strength indicator (RSSI) is monitored and if the value is lower than the previous measurement value, the reactance value of a variable reactance element is controlled, whereby impedance matching is performed (for example, refer to patent document 1). Accordingly, if impedance mismatching with an antenna occurs because of the effect of a nearby body and the RSSI lowers, impedance matching is automatically performed, so that the RSSI can be recovered. For a transmitter, for example, similar automatic impedance matching is possible by applying control for minimizing reflection electric power obtained through a directional coupler from a transmission antenna
A control circuit, an optimization algorithm, an evaluation function, and the like used for the automatic matching are proposed (for example, refer to non-patent document 1).    Patent document 1: JP-A-61-135235    Non-patent document 1: OGAWA Koichi and other three persons, “Automatic Impedance Matching of an Active Antenna Near the Human Operator by the Steepest Gradient Algorithm,” The transactions of the Institute of Electronics, Information and Communication Engineers, The Institute of Electronics, Information and Communication Engineers, September 2004, Vol. J87-B, Number 9, pp. 1287-1298